Instrument dial illuminator



Sept. 22, 1959 STEVENS 2,905,807

INSTRUMENT DIAL ILLUMINATOR Filed March' 29, V1956 I 25 24 I 25 3! Fig.1. SE -30 32 I j 35 2 2 swTe 15 -2 l 17 L16 29/- 4 I I; 2 2 15 I3 21 I9 A TTOR NE Y 2,905,807 INSTRUMENT DIAL ILLUMINATOR Bertram Stevens, Durham City, England, assignor to Thorn Electrical Industries'Limited, London, England Application March 29, 1956, Serial o. 574,746 Claims priority, application Great Britain April 4, 1955 7 Claims. (Cl. 240-816 The present invention relates to electriclighting fittings and is concerned with the illumination of instrument dials and the like.

The principal object of the invention is to provide .a lighting fitting of improved construction which is inexpensive to manufacture and nevertheless. eflicient in op eration.

According to the present invention a lighting fitting for the illumination of an instrument dial or the like comprises a metal shell adapted to accommodate an electric lamp and having an aperture through which light from the lamp can pass, a floating annular member adapted to pass the upper part of the lamp but to be engaged by a rim on the lamp cap, a supporting member adapted to be mounted upon a panel or upon'the frame of the instrument dial to be illuminated, means whereby the metal shell can be detachably mounted upon the supporting member, and a spring adapted to surround at least part of the lamp cap and to exert pressure between the metal shell and the floating member.

A light filter of annular shape may be arranged within the metal shell in order to impart a desired colour, say red, to the light emerging through the'a'perture.

The fitting preferably comprises a contact member adapted to make electric contact with the center of the lamp, this member passing through and being insulated from the supporting member. 1 "i The means for detachably'm'oun'ting the metal shell upon the supporting member may comprise a flange on one of these parts provided with a plurality of slots and on the other of the parts lugs adapted to pass through the slots and, upon relative rotation of the parts, to engage behind the flange. There may be three slots (and three co-operating lugs) unevenly spaced in order to ensure proper location of the light-passing aperture relatively to the supporting member. The said spring may be arranged to exert pressure between the slots and the lugs in order to assist in the secure retention of the metal shell.

The invention will be described by way of example with reference to the accompanying drawing in which Fig. 1 is a view in longitudinal section of one embodiment,

Fig. 2 is a view in cross-section on the line 2--2 of Fig. l, and

Fig. 3 is a view in longitudinal section of another embodiment of the invention.

Referring to Figs. 1 and 2, this embodiment is adapted to be mounted upon a sheet 10 which is one of two sheets 10 and 11, for example of metal, fixed together with a space between them which serves as a cable duct. For convenience in description the sheets will be assumed to be horizontal and that upon which the electric fitting is mounted will be assumed to be the upper sheet.

The supporting member is a metal annulus 12 having an inwardly directed flange 13 and outwardly-directed lugs 14 near its base and a number of downwardly-projecting lugs 15. The annular base of the member is mserted in an aperture in the sheet 10 and the lugs 15 are bent over outwardly to clasp the sheet between the lugs and the outwardly-directed flange 14.

An insulating sleeve 16 shaped to fit snugly within the supporting member has a shoulder bearing upon the inwardly-directed flange 13. At the upper end of the supporting member 12 are an outwardly-directed flange 17 and a number of upwardly-extending lugs 18 which can be bent over inwardly upon the insulating sleeve 16 to hold this sleeve firmly within the supporting member 12., Instead of using lugs the upper edge as a whole may be spun or otherwise turned over onto the sleeve.

A contact button 19 having a shank portion and a head 20 of larger diameter than the shank portion is arranged with the shank portion fitted snugly Within the insulating sleeve 16 which is counter-bored at its upper end to admit a part of the head. The insulating sleeve 16 has an upwardly-extending ridge 16 projecting beyond the upper surface of the head 20 in order to reduce the risk of shortcircuit between the button 19 and supporting member 12.

A metal shell 23 of cylindrical shape with its upper end closed has a shoulder 24 about half way along its length, this shoulder separating the upper portion from the lower portion which has the larger diameter. Within the upper portion is an annular filter 25 and this portion is suitably apertured at 26 to allow light from a p'ea lamp 27 within the shell to fall at the desired angle upon a dial to be illuminated. I

The outwardly-directed flange 17 at the top of the supporting member is provided with three unequally-spaced slots 28 (Fig.2) and three inwardly-turned lugs 29 on the bottom edge of the metal shell 23 are'adapted to engage in these slots. Within the metal shell 23 is a helical spring 30 bear: ing at its upper end upon a washer 31 which in turn :i bears upon the shoulder '24 in the shell and upon the lower end of the filter 25. The lower end of the spring 30 bears upon a floating annular sleeve 32 having an outwardly-turned flange 33. This sleeve is adapted to pass the upper part of the pea lamp 27 and cap 34 but to be engaged by the outwardly extending rim 35 of the lamp.

Electric connection is made with the lamp cap 34 through the floating member 32, the spring 30, the metal shell 23 and the supporting member 12 either to the upper metal sheet 10 or to a separate conductor. Connection with the center contact of the lamp is made through the button 19.

The spring 30 performs several functions. Before the lamp is inserted and when the metal shell 23 has been removed from the supporting member 12, the spring presses the floating member 32 against the top of the lugs 29. The lamp can then readily be inserted and is held upright by the filter 25 and the floating member 32. The spring holds the filter in place and also exerts force at the joint between the flanges 17 and lugs 29 when the metal shell is in position and thus tends to make this joint secure. The spring also exerts suitable contact pressures to ensure good electric contacts.

In the second embodiment to be described with reference to Fig. 3, the supporting member is a metal ring 36 having outwardly-extending flanges 37 and 38 at its top and bottom and an inwardly-extending flange 43 at its bottom. This supporting member is adapted to be mounted upon the frame 39 of an instrument whose dial 40 is to be illuminated. One of the screws normally provided for securing this frame to a panel 41 is replaced by a screw 42 whose head seats upon the inwardlyextending, flange 43 of the supporting member. The screwfhas an axial hole through which an insulated cable is passed, the conductor of the cablebeing connected'to a metal eyelet 45 fixed in the centre of an insulating disc '46. The disc seats in a" shallow recess lathe-head of the screw. The'rim of the recess is turned inward to retain the disc'in position. Beneath the disc the head'is hollowed to'accommodate insulating material 47which surrounds the end of the cable 44'. The disc 46 is provided with a ridge 46' for the same punposeias the'ridge '16 on: Fig. '1.

The screw described passes through the frame wand.

panel '41"'and is"secured by a nut 48 'onthe backiof'the panel: In this way the supporting member is fixed to the instrument frame. The eyelet45' makes'electric con tact with the-centre contact on the lamp 27.

The-remainder of this embodiment is constructed as described with reference to Figs. 1 and 2.

The embodiments above described are illustrative but not restrictive of the invention, which is defined in the following claims.

Iclaimr l. 'A lighting fitting for illuminating an, instrument dial comprising'a-hollow metal shell member foraccommodating an electric lamp havinga lamp cap provided with a projecting rim, a floating annulus having a'central portion for engaging the lamp cap and a flange portion projecting outwardlyfrom said central portion and positioned to be engaged by saidrim, a supporting member, electrical contact-making means in said supporting member, means at-oneendof said shell member for detachably' ingacolore'd light filter within said metal shell member,

said metal shell member having a closed endand-said light filter being retained at one end by said closed *end and at the opposite end by said spring.

=3. Alighting fitting according to claim I, said securing means comprising a slotted flange on one of said mmb'ersnna on the'other of said members lugs located 'ly projecting means remote from said compression spring,

and'ssaid-ispring thereby 'exerting pressure between said outwardly and inwardly projecting means.

5. A lighting fitting according to claim 1 comprising 1 a projecfion'within said metal shell member, said other endof said i'sprin'g 'engaging said projection.

6. A lighting fitting ion-illuminating an instrument dial comprising 'a'hollow metal shell member for accommodating an electric lamp having a lamp cap provided with a central contact and a projecting rim, a floating annulus positimedLtobe engaged'by said rim, a supportingzmember, meansatone'end of said shell mem her for detachably securing said metal shell on said supporting member, acompression spring positioned to surround at leastrapartzef saidlamp and engaging atone end thereof 'the-sidehof said floating annulus remote from said one end of said shell member aand engaging atsflierotherend .thereof upon/said metal shell member, the 'spnhgttherebvexerting ipressure between said metal shellandsaiiisfloating.anmirlus,r and electrical contacting means iorzmals'ing'electrical connection withsaid central contact, said supportingmeans comprising a hollow fixing bolt-'having/said electrical contacting means insulatingly mounted in tbeehead thereof.

.17.;:-A lightingfitting according'to claim 6, further comprising; an insulated: electrical conductor passing through said hollowvbolt andconnected to said electrical contasting meanse I References- Cited in the fileof this patent i frrnosrnrns PATENTS 17783135; 'peu 1as. on. 14, 1930 1,905,411 Kent et ale- Apr. 25, 1933 2256;61011] 'Greenlees Sept. 23, 1941 25371362 Roper n May 5,. 1.953 2,677,045 MacArthur c. Apr. 27, 1954 a l- .63s

l-larrtingtpnet al, Sept. 20, 1955 

